Circuit breaker



Aug. 17, 1937. H. J. cRABBs ET AL CIRCUIT BREAKER Filed Aug. 30, 1954 2Sheets-Sheet 1 RMI NNE

Filed Aug. 50, 1934 wlTNEssEs; l lNvENToRs 229 Heie/'t J'las and 243farq. i/g/oom.

`\24/ ATTORNE Patented lAug. 17, 1937 UNITED STATES YPATENT OFFICE -YRingbloom,

Turtle Creek, Pa.,

assignors to Westinghouse Electric & Manufacturing Company, EastPittsburgh, Pa., a corporation cf Pennsylvania Application August 30,1934, Serial No. 742,096

12 Claims.

Our invention relates to circuit interrupters and is particularlyconcerned with electrical switches of the type used for isolating orsectionalizing portions cf a transmission or distribution system.

Switches of this type are generally known as disconnecting switches andhave found wide application in present-day transmission and distributionsystems, both for the purpose of positively isolating certain equipmentor certain portions of a circuit, in order to permit maintenance work tobe done thereon, and for the purpose of interconnecting systems whichmeet at a common point such as a sub-station. Due

' to the large number of these devices which are used on even a smallsystem, it is desirable that they be relatively inexpensive tomanufacture.

At the same time, however, the safety of costly equipment and of theindividuals working on the line often depends entirely upon theswitches, and

it is imperative that they be absolutely safe and reliable in operation.

To further complicate the problem of providing an absolutely safe switchwhich shall not be unreasonably costly, disconnecting switches arefrequently mounted outdoors and are, therefore,

g subjected to extremely adverse weather conditions, particularly in thenorthern states where ice and sleet formations occur. As a result, acommercially successful device must be extremely rugged and must bepositively operable even when frozen or when wet, due to rain or othercauses. Further, it is also more or less common practice to mount theseswitches upon the tops of poles or upon sub-station structures, and itis, therefore, necessary that they shall be operable from one positionto the other by a hook-stick or similar device.

The principal object of our invention is to provide an improveddisconnecting switch which shall be inexpensive to manufacture,absolutely safe and reliable in operation, and which will be suitablefor applications wherein it must be mounted in a more or lessinaccessible place.

In the interests of safety, it is imperative that the blade structuresof switches of the type under consideration must be securely latchedagainst any movement which might be produced by magnetic stresses or thelike when the switch is in the closed-circuit position, and the onlysatisfactory method so far developed in the art for accomplishing thisis to provide a positive. latch which directly engages the bladestructure when the switch is in the closed-circuit position. Many 55 ofthe prior art latching arrangements are cornplicated, unreliable, andunduly costly, and the provision of an improved latching means fordisconnecting switches generally is another object of our invention.

A third object of our invention is to provide a disconnecting switchaccording to the abovementioned principal object which shall be providedwith an improved, positive latching means which shall be readilyreleasable by movement of the operating member during the initial stagesof the circuit-opening operation.

A further object of our invention is to provide an improvedhigh-capacity disconnecting switch which shall be provided with aplurality of separate blade assemblages and a plurality of separatelatching members, the entire structure being completely operable throughvthe movement of a single operating member.

Another further object of our invention is to provide a double-throwdisconnecting switch which shall be provided with a separate latchingmeans for holding the blade in either of the two positions of theswitch, and with means whereby th-e movement of a single operatingmemberv will eiiect the release of either of the latches.

An additional further object of our invention is to provide alatchingmeans for an electrical switch which shall be so positioned that it willnot be effected by the magnetic reactions set up when current flowsthrough the switch. Y

An ancillary object of our invention is to provide an improved latch foruse with disconnecting switches or other equipment which shall becam-operated.

These and other objects of our invention will be made more apparent inthe following description of a preferred embodiment of our invention.Referring to the drawings: ,Y

Figure 1 is an elevational view of a doubletnrow, multiple-bladedisconnecting switch wherein are embodied the principal elements of ourinvention;

Fig. 2 is a plan View of the switch structure shown in Fig. 1;

Fig. 3 is a front elevational view of the operating member used in theswitch shown in Figs. 1 and 2;

Fig. 4 is a side elevational View of the member shown in Fig. 3;

Fig 5 is a fragmentary perspective view showing the details of the latchand the switch operating member oi the switch illustrated in Vthe otheriigures of the drawings;

Fig. 6 is a fragmentary plan view of a single blade switch whichincludes the novel latching 'arrangement shown in the device illustratedin Figs. l to 5;

Fig. 7 is a front elevational. View of a modified switch operatingmember, particularly intended 5 for use with vertically mounted switchesof the type illustrated in the other figures of the drawings; and

Fig. 8 is a side elevational view of the member shown in Fig. '7.

l The preferred embodiment of our invention`VV comprises a base member Iwhich may be formed from a channel-shaped section of structural steel,or the like, three spaced insulators which are bolted onto thechannelshaped base I by suitable l5 stud bolts 3, a blade assemblage 1,a contact means !I, which includes a pair of spaced conn tact tonguesI2, for pivotally supporting the blade assemblage on the centralinsulatorl 5, and'two sets of spaced contact tongues I3 which areadapted to be engaged by the blade assemblage 1 when the switch is ineither of the two closedcircuit positions. Thecontact tongues I3 and thecontact` meansY II for pivotally supporting the blade assemblage arebolted to suitable cap members I5, one of which is rigidly aiiixed tothe v-upperend"of eachof the three insulators 5. A pair of latch `meansI1, each of which is supu ported upon one of the outer insulators 5, isprovided for latchingthe blade assemblage 1 in either of the two closedcircuit positions.

The blade assemblage 1 comprises two pairs of spaced parallel bladelelements 9, each of which is formed from a flat sheet of conductingmaterial, preferably copper. A suitable circular opening is punched inthe righahana @nu (Fig. 2 of each of the separate blade eiementsin orderto permit the passage therethrough of the bolts I9 which form thepivotal support `means for the blade assemblage proper. These boltsextend through similar openings vin the upstanding Ytongue portions I2which serve to support the blade means, and the contact pressure betweenthe inner opposed surfaces of each y, of the two sets of parallel bladeelements 9 and the cooper ating supporting tongue i2 is provided byspring washers 2I interposed between the bolt fastenings and the blades.

A second bolt 23 extends through each of the two parallel, bladesections adjacent the unpivoted end of the blade assemblage. These bolts23, in conjunction with spring washers 25, serve to provide the contactpressure between the blade elements 9 and the cooperating contacttongues I3 which are supported upon the outer insulators. A third bolt21 extends through each of the two sets of blade Velements 9 adjacentthe extreme outer end thereof, these bolts 21 serving as supports forthe operating member. 29, which is shown particularly in Figs. v andl.

Two pairs of diverging guide members 3I are bolted upon the cap portionI5 of each of the two outer insulators 5 for aiding in guiding themovement of the switch blade during'the operation of the switch, and thecontact tongues I3 are provided with suitable cut-out, portions 33for'aocommodatingthe bolts 23.

' A circular opening 35 is punched in the outer unpivoted end of each ofthe blade elements S in order that the blade assemblage may be latchedagainst movement when the switch is in either of the closed circuitpositions. While these openingsare shown in Fig. 5 as being formed inall four of the blade elements, this arrangement is followed onlybecause it permits the use of a standard blade element for each of thefour sepau rate blade sections, it being necessary to provide theopenings 35 only in the two inner blade elements.

Each of the two latching means I1 which cooperates with these openings35 in the blade elements comprises, as is shown particularly in Fig. 5,a pair of latch members 31, each of which is pivotally supported uponthe cap portion i5 of the associated insulator and is biased toward thelatched position. by a suitable coil spring 33. Each of the opposed sideportions 4I of the operating member 29 is provided with a projectingportion 43 having a cam surface 45 thereon, these portions 43 beingadapted to extend into the same openings in the. blade members which areen,- gaged by the latch members 31 when the switch is in the closedcircuit position (i. e., the openings 35,). The `dimensions `ci thelopenings 35, the latching members 31, and the cam portions 43 oftheoperating member 29 are so correlated that the latch members 31 maymove freely to the` fully latched position during the circuit-closingoperation without interference from the cam portions.

During the initial stages of the circuit-openingV operation, these camsurfaces 45 on the projecting portions 0.13 are adapted to engagecooperating cam surfaces d1 formed on the latch members 31 and to movethose members out of engagement with the cooperating openings 35 in. theblade elements 9, thereby effecting the unlatching of the bladeassemblage and permitting the switch to be moved to the open circuitposition. The movement of each of the latch members 31 toward thelatched lposition under the action of the associated biasing springs 39is limited through `the engagement of a projecting portion [is formedintegral therewith and the support therefor. It is necessary to limitthe motion of the latch in orderto assure that the switch shall berelatched during every closing operation.

The cap portion I5 of each of the three insulators 5 is provided with asuitable terminal member 5I in order to permit the switch to be readilyinterconnected into an electrical circuit. j

The switch is shown in one of the two closedcircuit positions in Fig. 1.To open the switch or to move the blade assemblage 1 tothe otherclosed-circuit position, a hoolesticl; or other degA.

vice is 'insertedintthe operatingreye 53 of the switch operating memberA2,9, and that member is v moved in a clockwise direction about itspivot.

point-the bolts21. This movement brings the cooperating cam surfaces`45pavnd I1orthelatch, members 31 and the projecting portions #13 ofthew operating member 29r (which portions extend into'.

the openings 35' formed in the bladeelements 9) into engagement witheach other, and when'the operating member 29 has been moved so that theprojecting cam kportions 4i3 engage the lower.Y side of the'cooperatingopenings 35 in the blade,

elements 9, the nadjacent latch members 3 1`have member 29.

It should bey notedthat the operatingmember 2S is ireely movableupoirthe bolts 21 which comprise the supporting means therefor, and it.is l'thus 'impossible to rotate the blade assemblage 1 until,theprojecting cam portions 43 of 'the'Y member 2,9 have been movedadistance suii-` cient to release'the Ylatches 31. .'Ihus, the releasecfthe latches 31 takes .place automatically during the initial stages ofthe opening operation, and it is not possible to rotate the bladeassemblage 'l until the latches 3l have been released.

By inspection of Figures l and 5, it Will be seen that the operatingmember 29 is movable a rather considerable amount with respect to theblade assemblage 'i during each opening operation of the switch, thelimits of this independent motion being defined by the engagement of thecam portions 43 with the sides of the circular openings 35. The camsurfaces 45 on the projecting portions i3 engage the cam surfaces tl sothat the release of the latches 3l is effected during the initialportion of movement of the operating member 29 independently of theblade assemblage l. rIhis arrrangement permits the latter portion or".this movement to be used for producing a vprying action on the bladeassemblage l which serves to start that assemblage in motion and therebyfacilitates the opening operation of the breaker. The reaction force ofthe latch biasing springs 39 is usually sufficient to initiate thisprying action, and in addition the heel portionat the lower end of eachof the latch members 3l opposite the projection 49 as shown in Fig. 5rigidly engages the adjacent plate on top of the cap member immediatelyfollowing the disengaging of the blade assemblage by the latch of whichit forms a part. lThese portions thus serve to provide steps for thelatches, and the maximum possible prying action necessarily results.

Following the release of the latch members 37, the blade assemblage maybe moved either to the open-circuit position or into engagement with theother set of contact tongues i3 supported upon the right-hand insulator.When the blade assemblage 'i is being moved into engagement g) witheither of the sets of contact tongues I3, it

is necessary to move the operating member 29 so that the projecting camportions 43 abut against the upper surfaces (with respect to the base I)of the openings 35 formed in the blade elements 9. This assures that thelatch releasing means is in a position Where it in no way interfereswith the latching movement of the latch members during the circuitclosing operation. Thus, as the blade assemblage is moved. into eitherof the two closed circuit positions, the latch members 3l automaticallyengage the blade assemblage, without interference from the latchreleasing means. The obvious result, of course, is to provide anabsolutely fool-proof structure which may not be operated in anincorrect or undesired manner.A When the blade assemblage is moved tothe closed-circuit position, it is positively latched in and the latchescannot be releaseduntil the operating member 29 is moved in the circuitopening direction.

The cam action of the operating member 2d andthe latches 3l isparticularly effective in breaking ice which may be formed on the switchduring the winter time, and for that reason little i) difficulty will beexperienced in operating the switchA under almost any conditions. Theouter end of'each of the two sets of parallel blade elements is free tomove iaterally on the bolts 21 which serve to support the operatingmember 29, and the switch is thus made full-oating, which means that theblade elements are capable or" movement toward each other in order tocompensate for wear, or the like, during its operation.

Two sets of parallel blades and two latches on each of the spacedconducting members have been shown in the'structure. Itis, ofcourse, acomparatively simple matter t`o utilizejalinost any number ofYblades,since the form of latchY release mechanism which we havedisclosedv lends itself readily to amultiple blade construction. It isalso possible to utilize only a single blade element, the-latchreleasing mechanism being very suitable for this type of switchy asWell. l

Each of the latch members 3'lfis movable ina plane whichis-substantially at rightfangles to the normal plane of movement of theblade means. Also, the entire latch structure is disposed outside of thespace between the tongues I2 and I3 and, therefore, out of the normalconducting path through the switch. By this arrangement, all magneticstresses on the latches which might be produced by very heavy overloadcurrents flowing through the switch are entirely obviated andanabsolutely safety operation is assured under all possible conditions; Ifdesired, the latch struc-v ture may be insulated from the stationarycontact portion, but this is not absolutely necessary, since the rightangle disposition of the paths of move-v ment of the latch and thebladeJ obviates any possibility of the latch vbeing opened Vwhen theswitch is in operation. n

The structure shown in Fig. 6 is essentially similar to that shown inthe other gures of the drawings, except that aA singlepair of parallelblade elements have been utilized. When this is done, it is of course,unnecessary tov utilize a bifurcated operating member. The blade ele"-ments I |19 are essentially similar in form to those shown in thepreviously described device. The operating member |29 is pivotallysupported upon a bolt |21 which extends through both of the' opposedblade elements. The latch |31 engages an opening |35 in the side ,of oneof the blade elements and is movable Substantially'Y at right angles tothe plane of movement ofthe blade assemblage, and both of the bladeelements are full-floating. The construction of the guide horn |3|, andthe single bolt I 23 and the two spring washers |25 for securingcontactpressure be-V tween the inner surfaces of the blade means and thecooperating contact tongue ||3 are substantially similar to those in thestructure already described.

The modied operatingV member 229 shown in Figs. 7 and' 8 is particularlyintended'for use with vertically mounted, single vthrow switches. Bypositioning the eye portion 253 at an angle, ,withv respect to the shankportion 24|, the engagement of the operating member by the hook stick'or otheruevice is greatly faciiitatedndtne effective leveragev of theoperating member is increased.4 This modiedstructure is provided withapro#y jecting portion 243 and a cam surface 245, 'which' correspond tothe portions 43and 45 of the mem# ber 29.

In the foregoing we have described the struc-V tural features'and themodevof operation of a novel disconnecting switch which possessesnumerous advantages over the structures previously known in the art. Ourimproved switch utilizes an improved latching arrangement whichpositively latches theblade against movement when the switch is in theclosed circuit position, vbut which is readily releasable bythe initialmove` ment of the operating member duringthe circuit opening operation,Qur improved latc'liin'g'fmeans moves in aidirectio'n at rightangles.to'the nor'- mai piane of Vmotion of the biade and thereby assures thatthe'v magnetic reactions ySet up bythe now of current through the'switch shall not reiec'zt Aany'undesired release of the blade by thelatching subjected to a prying action by the movement of the latchreleasing means during each opening operation of the switch. Also ourimproved latch is particularly suitable for use with double-throwswitches, the same latch releasing means being adaptable to operateseparate latches disposed adjacent either of the two cooperatingcontacts for the blade means.

While in accordance with the patent statutes we have disclosed thestructural features of a preferred embodiment of our invention, it is tobe understood that many of the principles disclosed are capable of wideapplication without departing from the principles of the invention. Itis our desire, therefore, that the language of the accompanying claimsshall be accorded the broadest reasonable construction and that ourinvention shall be limited only by what is expressly stated therein andby the prior art.

We claim as our invention:

l. In an electric switch, a pair of spaced conducting members, aVmovable blade means for cooperating therewith to open and to close theelectricalY circuit through said switch, at least a portion of saidblade means having an opening formed therein, an operating membersupported on said blade member, and a single latch member having alportion which is adapted to engage said opening when said blade means isin the closedcircuit position, said operating member having a portionwhich extends into said opening for directly engaging and moving saidlatch member to eifect the release of said blade means during eachopening operation of said switch.

2. In an electric switch, a pair of spaced insulators, a blade meanssupportedfor swingable movement upon one of said insulators, cooperatingcontact means supported on the other of said insulators, said blademeans comprising a flat plate of conducting material kwhich is providedwith a cutout portion adjacent one end thereof, a single, pivoted latchsupported on said other insulator and movable to engage said cutoutportion when said blade means is in the closed-circuit position, and anoperating member which is supported on said blade means adjacent saidcutout portion and which is provided with a portion adapted to extendinto said cutout portion for directly engaging and-moving said latch toeffect the release of said blade means during each opening operation ofsaid switch.

3. In an electric switch, spaced contact'members, a flat blade pivotallysupported upon one of -said contact members for swingable movement intoand out of engagement with said other contact member, said blade havingan opening cut therein adjacent the unsupported end, a single latchmember pivotally supported adjacent said other contact member andmovable substantially at right angles to the normal plane of movementofthe blade member to engage the cutout portion and thereby restrainsaid blade member against movement, means biasing said latch member tothe latched position and an operating member supported on said blade,said operating member having a portion extending into said opening whichportion is provided with a cam surface for directly engaging a similarcam surface forming a part of said latch member, said cam surfaces beingso arranged that said latch member is moved by said operating member soas to release said blade during the initial stages of the switch openingoperation.

4. In a double-throw electric switch, a pair of spaced conductingmembers, a blade means movable into and out of engagement with either ofsaid conducting members for opening and for closing the electricalcircuit through said switch, at least aportion of said blade meanscomprising means having an opening formed therein, an

operating member supported upon said blade member, and a single latchmember which is supported adjacent each of said spaced conductingmembers, each of said latch members being individually adapted to engagesaid opening when said blade means has been moved into engagement withthe adjacent conducting member, said operating member having a portionwhich extends into said opening for directly engaging and moving theadjacent latch member to effect the release of said blade means duringthe initial stages of each opening operation of said switch. 5. In anelectric switch, a plurality of separate blade members, means forsupporting said blade members adjacent one end thereof for swingablemovement to open and to close the electrical circuit through saidswitch, at least some of said blade members having openings cut thereinadjacent their unsupported ends, a plurality of separate latch members,each of which is adapted to engage one of said openings when said switchis in the closed-circuit position, and a single operating membersupported upon said blade members for simultaneously moving all of thosemembers during the operation of said switch, said operating memberhaving portions which are adapted to extend into said openings in saidblade members for directly engaging and moving the adjacent latch memberto effect the release of said blade members by said latch members duringthe initial stages of each switch-opening operation.

- 6. In a double throw switch, a pair of spaced conducting means, acooperating blade means which comprises a plurality of separate.l blademembers, means for supporting said blade members adjacent one endthereof for swingablev movement to open and to close the electricalcircuit through said switch, at least some of said blade members havingopenings cut therein adjacent their unsupported ends, a plurality ofseparate latch members one of which is adapted to engage one of saidopenings in said blade members when said blade means has been moved intoengagement with either of said spaced conducting means, and a singleoperating member supported upon said blade members for simultaneouslymoving all of those members during the operation of said switch, saidoperating member having portions which are adapted to extend into saidopenings in said blade members directly engaging and moving the adjacentlatch member to effect the release of said blade members by said latchmembers during the initial stages of each switch-opening operation,regardless of which closed circuit position said blade means is in atthe beginning of the switch-opening operation.

'7. In an electric switch, a pair of spaced conducting members, amovable blade member for 'cooperating therewith to open'and to close theelectrical circuit through said switch, at least a portion of sain blademember having an opening formed therein, operating member supported uponsaid blade member so as to be movable a predetermined distance withrespect thereto, and a latch means having a portion which is adapted toengage said opening when said blade member is in the open circuitposition, said operating member having a portion which extends into saidopening for automatically effecting the release of said latch means andfor producing a prying action tending to initiate the movement of saidblade member toward the open circuit position during each operation ofsaid switch.

8. In an electric switch, a pair of spaced conducting members, a movableblade member cooperating therewith to open and to close the electricalcircuit through said switch, said blade member comprising asubstantially iiat plate of conducting material which is movable in aplane substantially parallel to the opposed faces thereof, and which isprovided with a cutout portion adjacent one end thereof, a latch meanshaving a portion adapted to extend into said cutout portion when saidblade is in the closed circuit position, and an operating member whichis pivotally supported on said blade member so as to be movable apredetermined distance with respect thereto, and which is provided witha portion which extends into said cutout portion for automaticallyeiiecting the release of said latch means and for exerting a pryingaction tending to initiate movement of said blade member toward the opencircuit position during each operation of said switch.

9. In an electric switch, spaced contact members, a substantially :datblade member supported upon one of said contact members for swingablemovement into and out of engagement with the other contact member, saidblade member havin;Y an opening cut therein adjacent the unsupportedend, a latch member supported adjacent said other contact member andmovable substantiallv at right angles to the normal plane of movement ofsaid blade member to engage said opening, and an operating membersupported on blade so as to be movable a predetermined amount withrespect thereto, said operating member having a portion extending intosaid openin T for engaging said latch member in order to eiiect itsrelease when said operating member is moved relative to said blademember during each opening operation of said switch, said operatingmember causing said latch member to release said blade member during theinitial portion of its possible movement relative to said blade member,and, during the iinal portion of its possible movement with respect tosaid blade member, exerting a prying action tending to initiate movementof said blade member toward the open circuit position.

l0. In an electric switch, a pair oi spaced conducting members, asubstantially flat blade member which is supported for swingablemovement in a substantially fixed path, for cooperating therewith toopen and to close the electrical circuit through said switch, said bladehaving an opening cut therein adjacent the unsupported end, a latchmember supported adjacent one of said contact members and movable atsubstantially right angles to the normal plane of movement of theblade'member to engage said cutout portion and thereby restrain saidblade member against movement, means biasing said latch member `to thelatched position, and an operating member supported upon said blade soas to be vmovable a predetermined amount with respect thereto, saidoperating member having a portion extending into said opening, whichportion is provided with a cam surface for cooperating with a similarcam surface forming a part of said latch member in order that said latchmember shall be moved so as to release said blade member when saidoperating member is moved relative to said blade member during eachopening operation of said switch, said operating member causing saidlatch member to release Said blade member during the initial portion ofits possible movement with respect to said blade member, and, during thefinal portion of its possible movement with respect to said blademember, exerting a prying action tending to initiate movement of saidblade member toward the open circuit position.

ll. In a double throw electric switch, a pair of spaced Contact members,a pivotally supported blade which is swingable into and out ofengagement with either of said Contact members, said blade having anopening cut therein adjacent the unsupported end, a pivotally supported,spring biased latch positioned adjacent each of said spaced Contactmembers and movable substantially at right angles to the normal plane ofmovement of said blade, either of said latch members being adapted toengage said cut-out portion and thereby restrain said blade frommovement when that member has been moved into engagement with either ofsaid Contact members, and an operating member supported upon said bladeso as to be movable a predetermined amount relative thereto, saidoperating member having a portion extending into said opening, whichportion is provided with a cam surface and is adapted to cooperate witha similar cam surface forming a part of each of said latch members, saidopening being of sufficient size that the initial movement of saidoperating member relative to said blade during each opening operation ofsaid switch effects the release of the adjacent latch member and thefinal portion of the possible relative movement of said latch memberwith respect to said blade member produces a prying action tending toinitiate movement of said blade member toward the open circuit position.

l2. In an electric switch, a pair of spaced, stationary insulatorcolumns, a Contact supported upon one'oi' said insulator columns, asubstantially flat blade pivotally supported upon the other of saidinsulator columns for swingable movement into and out of engagement withsaid contact to open and to close the electrical circuit through saidswitch, said blade having an opening cut therein adjacent theunsupported end, a pivotally supported spring biased latch positionedadjacent said contact member and movable substantially at right anglesto the Y normal plane of movement of said blade to engage said cut-cutportion and thereby restrain said blade against movement, and anoperating lever pivotally supported intermediate its ends upon saidblade and movable a predetermined amount with respect thereto, saidoperating lever having an outwardly projecting portion, formed integraltherewith, which extends into said opening from the side opposite tothat which said latch enters, this portion having a cam surface forcooperating with a similar cam surface forming a part of said latchmember in order that said latch member shall be moved so as to releasesaid blades when said operating lever is Y moved relative to said bladeduring each opening operation of said switch, said operating levereffecting the release of said latch during the initial portion of itspossible movement with respect to said blade and, during the nal portionof its movement with respect to said blade, exerting a prying actiontending to initiate movement of 5 said blade toward the open circuitposition.

HERBERT J. CRABBS. CARL A. RINGBLOOM.

